1. Field of the Invention
The present invention relates to a pump and a fuel cell system using the same, and more particularly to, a pump having a noise suppression and vibration proof structure capable of significantly reducing vibration and noise caused by the pump through the improvement of a fixed structure and a pump housing structure and a fuel cell system using the same.
2. Discussion of Related Art
A fuel cell is a power generation system for directly converting chemically reactive energy of hydrogen and oxygen contained in hydrocarbon series material such as methanol, ethanol, and natural gas into electric energy.
The fuel cell is divided into a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, a polymer electrolyte membrane fuel cell, and an alkaline fuel cell in accordance with the kind of used electrolyte. Each fuel cell operates by the same principle, however, varies with the kind of used fuel, operation temperature, catalyst, and electrolyte.
Among the above fuel cells, the polymer electrolyte membrane fuel cell (PEMFC) has an output characteristic remarkably higher than the output characteristics of the other fuel cells, operates at low temperature, has fast starting and response characteristics, and is widely used for a dispersive power source such as a static power station of a house and a public building as well as a portable power source such as a portable electronic apparatus and a transportable power source such as a vehicle power source.
The above-described PEMFC includes a stack, a reformer, a fuel tank, and a fuel pump. The PEMFC supplies the fuel in the fuel tank to the reformer by the operation of the fuel pump. The reformer reforms the fuel to generate hydrogen gas. In the stack, the hydrogen gas and the oxygen electrochemically react to generate electric energy.
Also, the fuel cells include a direct methanol fuel cell (DMFC) that is similar to the PEMFC and that can directly supply liquid methanol fuel to the stack. Since the DMFC does not use the reformer unlike the PEMFC, it is advantageous to making the size of the DMFC small.
The fuel cell stack commonly has a structure in which several or several tens of unit fuel cells each comprised of a membrane electrode assembly (MEA) and a separator are stacked. Here, the MEA has a structure in which an anode (also referred to as a negative electrode) and a cathode (also referred to as a positive electrode) are attached to each other with a polymer electrolyte membrane interposed. The fuel cell stack is compressed and sealed up in order to remove non-uniform operation conditions such as the pressure drop in the stack or the decrease of the concentration of oxygen. FIG. 1 schematically illustrates the operation principle of a common fuel cell including the polymer electrolyte membrane. Referring to FIG. 1, a MEA 20 of a fuel cell 10 includes a polymer electrolyte membrane 12, an anode catalyst layer 14, and a cathode catalyst layer 16. When the fuel containing the hydrogen gas or hydrogen is supplied to the anode catalyst layer 14 in the fuel cell 10, electrochemical oxidation occurs in the anode catalyst layer 14 so that ionization and oxidation are performed to generate hydrogen ions H+ and electrons e−. The ionized hydrogen ions are transmitted from the anode catalyst layer 14 to the cathode catalyst layer 16 through the polymer electrolyte membrane 12. The electrons are transmitted from the anode catalyst layer 14 to the cathode catalyst layer 16 through an external wiring line 18. The hydrogen ions transmitted to the cathode catalyst layer 16 perform electrochemical reduction on the oxygen supplied to the cathode catalyst layer 16 to generate heat and water. Electrical energy is generated by the transmission of the electrons.
The electrochemical reactions of the PEMFC and the DMFC will be represented as follows in EQUATIONS 1 and 2, respectively.ANODE: H2→2H++2e−CATHODE: ½O2+2H++2e−→H2O  [EQUATION 1]ANODE: CH3OH+H2O→CO2+6H++6e−CATHODE: 3/2O2+6H++6e−→3H2O  [EQUATION 2]
The fuel cell system may be divided into an active fuel cell system that supplies fuel and air containing hydrogen to a fuel cell stack through the operation of a fuel pump and an air pump and a passive fuel cell system that supplies fuel or air without using a pump.
The output of the active fuel cell system is higher than the output of the passive fuel cell system. However, since the fuel cell stack is compressed and sealed up with a plurality of fuel cells stacked, the fuel cell stack has predetermined internal pressure. Therefore, in order to supply an enough amount of air to the fuel cell stack with the predetermined internal pressure considering oxygen depletion, a high output air pump must be used. As described above, the high output air pump must be used for the conventional active fuel cell system so that large noise and vibration are generated.
Also, the conventional active fuel cell system commonly includes at least one fuel pump other than the air pump. In this case, the fuel pump in the conventional active fuel cell system additionally generates noise and vibration.
The noise and vibration of the pumps causes user to be discomfort during the continuous operation of the fuel cell.
Furthermore, when the active fuel cell system is used as a power source supply device of each of electronic apparatuses such as a notebook computer, a portable multimedia player (PMP), a portable digital video disc (DVD) player, a personal digital assistant (PDA), a mobile telephone, and a camcorder, the noise and vibration of the fuel cell system make users uncomfortable. Therefore, in order to make the users comfortable and to facilitate the use of the electronic apparatuses, the generation of the noise of the fuel cell must be prevented.